Grand Seiko STGK031
Ref. STGK031 · In production
- Case30 mm
- Thick10.5 mm
- Lug-to-lug36.2 mm
- Water res.100 m
- MovementAutomatic
- CrystalSapphire
Overview
The Grand Seiko STGK031 is a sports watch from the Heritage collection, part of the 62GS Mechanical 30mm family. It has a 30 mm stainless steel case, 10.5 mm thick, 36.2 mm from lug to lug. Inside is a automatic movement (calibre 9S27) with 50 h of power reserve. You also get 100 m water resistance, a sapphire crystal and a bracelet.
Who it suits
- Wrists of roughly 12.1–13.6 cm (4.8–5.4 in), by our Watch Finder sizing guide
- Everyday wear including swimming
- Shirt cuffs and smarter dress codes
- People who enjoy seeing a mechanical movement at work
Strengths
- Sapphire crystal resists scratches
- Slim at 10.5 mm
- Compact 36.2 mm lug-to-lug suits smaller wrists
- Display caseback shows the movement
- Light at 79 g
Written by Watch.co from the published specs below. These are not owner reviews.
Full specifications
Case
| Case diameter | 30 mm | grand-seiko.com · 23 Oct 2026 |
|---|---|---|
| Thickness | 10.5 mm | grand-seiko.com · 23 Oct 2026 |
| Lug-to-lug | 36.2 mm | grand-seiko.com · 23 Oct 2026 |
| Case material | Stainless steel | grand-seiko.com · 23 Oct 2026 |
| Crystal | Sapphire | grand-seiko.com · 23 Oct 2026 |
| Anti-reflective coating | Anti-reflective coating on inner surface | grand-seiko.com · 23 Oct 2026 |
| Caseback | Display (see-through) | grand-seiko.com · 23 Oct 2026 |
| Water resistance | 100 m | grand-seiko.com · 23 Oct 2026 |
| Magnetic resistance | 4,800 A/m | grand-seiko.com · 23 Oct 2026 |
| Weight | 79 g | grand-seiko.com · 23 Oct 2026 |
Movement
| Movement type | Automatic | grand-seiko.com · 23 Oct 2026 |
|---|---|---|
| Calibre | 9S27 | grand-seiko.com · 23 Oct 2026 |
| Made in-house | Yes | grand-seiko.com · 23 Oct 2026 |
| Power reserve | 50 h | grand-seiko.com · 23 Oct 2026 |
| Hand-winding | Yes | grand-seiko.com · 23 Oct 2026 |
Strap / Bracelet
| Bracelet / strap | Bracelet | grand-seiko.com · 23 Oct 2026 |
|---|---|---|
| Lug width | 15 mm | grand-seiko.com · 23 Oct 2026 |
Other
| US list price (MSRP) | $6,600 | grand-seiko.com · 23 Oct 2026 |
|---|---|---|
| Production status | In production | grand-seiko.com · 23 Oct 2026 |
| Style (our classification) | Sports | our classification |
Specs are summarised in our own words from the brand's product page. Each row links its source and the date we checked it. Fields we haven't verified are left out rather than guessed.
Variants with the same specs
Same case, movement and bracelet or strap; typically a different dial or finish.
More in 62GS Mechanical 30mm
Similar alternatives
Picked with Watch Finder's style tags and sizing.
Questions about the Grand Seiko STGK031
How big is the Grand Seiko STGK031?
The case is 30 mm wide, 10.5 mm thick and 36.2 mm from lug to lug.
What movement does the Grand Seiko STGK031 use?
It uses the 9S27 calibre, a automatic movement with 50 h of power reserve.
Can I swim with the Grand Seiko STGK031?
Yes. It is rated to 100 m.
How much is the Grand Seiko STGK031?
The US list price was $6,600 on grand-seiko.com when we checked on 23 Oct 2026. Prices change, so check before you buy.
Will the Grand Seiko STGK031 fit my wrist?
By our sizing guide it sits best on wrists of about 12.1–13.6 cm (4.8–5.4 in). Use the fit checker on this page to test your own wrist.
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